Fix background compilation queue access. Some cleanups.

runtime/vm/compiler.h

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_COMPILER_H_
 #define VM_COMPILER_H_
 
 #include "vm/allocation.h"
 #include "vm/growable_array.h"
 #include "vm/runtime_entry.h"
@@ skipping 138 matching lines @@
   static void AbortBackgroundCompilation(intptr_t deopt_id);
 };
 
 
 // Class to run optimizing compilation in a background thread.
 // Current implementation: one task per isolate, it dies with the owning
 // isolate.
 // No OSR compilation in the background compiler.
 class BackgroundCompiler : public ThreadPool::Task {
  public:
+  virtual ~BackgroundCompiler();
+
   static void EnsureInit(Thread* thread);
 
   static void Stop(BackgroundCompiler* task);
 
   // Call to optimize a function in the background, enters the function in the
   // compilation queue.
   void CompileOptimized(const Function& function);
 
   void VisitPointers(ObjectPointerVisitor* visitor);
 
@@ skipping 11 matching lines @@
   Monitor* done_monitor_;   // Notify/wait that the thread is done.
 
   BackgroundCompilationQueue* function_queue_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(BackgroundCompiler);
 };
 
 }  // namespace dart
 
 #endif  // VM_COMPILER_H_